Contamination Control for Liquid Handling

ABSTRACT

A structure for holding sample-containing receptacles includes a cover with holes formed therein through which the receptacles can be accessed with a substance transfer mechanism, such as a robotic pipettor. When the transfer mechanism is inserted into and then withdrawn from a receptacle, a string of viscous material may be suspended from the mechanism. A viscous string removal element adjacent each opening engages the string of viscous material and dislodges the string from the mechanism when the mechanism moves in a prescribed path with respect to the removal element. A sample rack configured to hold receptacles and to be inserted into the structure below the cover includes a sample rack having receptacle-receiving pockets, each with a resilient element and a positioning feature for holding receptacles of varying sizes in a predetermined position within the receptacle receiving pocket, and a cover including features for preventing a receptacle from being pulled out of its receptacle-receiving pocket when the transfer mechanism is withdrawn from the receptacle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Application No. 61/178,652, filed May 15, 2009, thedisclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field of the Invention

This invention relates to systems, methods, and apparatus for storingand presenting sample materials for access by a sample transferapparatus and for limiting the incidence of cross-contamination betweensample-containing vessels during a sample transfer operation.

2. Background of the Invention

All documents referred to herein, or the indicated portions, are herebyincorporated by reference herein. No document, however, is admitted tobe prior art to the claimed subject matter.

Analyzers for performing assays on fluid samples typically include afluid transfer mechanism for transferring fluid sample material andother fluids between various receptacles or containers. For example,fluid sample material may be introduced into the analyzer via a samplereceptacle, such as a test tube, containing an amount of the fluidsample, placed in the analyzer or in operative proximity to theanalyzer. The analyzer may include an automated fluid transfer mechanismcomprising a robotically-controlled pipetting device having anaspirating probe for accessing the contents of a receptacle. The probemay comprises a barrel with a protective tip (e.g., a pipette tip)mounted (e.g., frictionally) on its distal end.

Fluid sample material is transferred from the sample receptacle bypositioning the aspirating probe above the sample receptacle and thenlowering the probe until a distal end of the probe is submerged in thefluid sample material held in the container. After the probe issubmerged, an amount of fluid is drawn into the probe. The probe is thenraised and moved to another location within the analyzer and isoperatively positioned above another container (or, alternatively, theprobe can be held in a fixed position and the sample receptacle andother containers can be moved relative to the probe). The samplematerial may be transferred to a reaction receptacle (e.g., test tube,cuvette, microtiter plate well, etc.) within which the sample materialis combined with reagents and/or other reactants (and, optionally, thecontainer and its contents may be subjected to other conditions orstimuli, such as, incubation at an elevated temperature, mixing, and/orcentrifuging) to effect a transformation or chemical, biochemical orbiological reaction. After the probe is positioned above the containerthat is to receive the sample material, some or all of the fluid isdispensed from the probe into one or more containers, moving the probefrom receiving container to receiving container as necessary.

During such a fluid transfer procedure, care must be taken to avoidcross-contamination due to spilled or misplaced sample material. Forexample, sample from one sample receptacle should not be mistakenlydeposited into another sample receptacle containing a different sampleor a sample from a different source. Similarly, no sample materialshould be deposited into a reaction receptacle in which such sample isnot intended, for example in a reaction receptacle within which adifferent sample had already been dispensed.

Fluid sample material may include, for example, urine, blood, plasma,saliva, mucus, seminal fluid, amniotic fluid, cerebrospinal fluid,synovial fluid, and cultures. Such materials may, under certaincircumstances or conditions, be characterized as having a viscousconsistency. Accordingly, when the probe of a pipetting device issubmerged into the sample material and is then withdrawn, the viscous ormucoid nature of the sample material may result in a string of viscousmaterial suspended from a distal end of the probe after the probe iswithdrawn from the sample receptacle. Further movement of the sampletransfer probe may drag the string of viscous material along with it,thereby potentially causing cross-contamination should the string ofviscous material contact or fall into another sample receptacle orreaction vessel or other contamination-sensitive surface or componentwithin the analyzer.

SUMMARY OF THE INVENTION

The present invention provides methods, systems, and apparatus forremoving a string of viscous material from the probe of a fluid transfermechanism in a controlled manner so that the string is detached from theprobe in a location that is unlikely to cause cross-contamination.

Aspects of the invention are embodied in a method for separating aviscous material suspended from a probe of an automated pipettor. Theprobe is lowered into a receptacle containing a viscous material throughan opening formed in a cover disposed over the receptacle. At least aportion of the viscous material is drawn into the probe. The probe fromis then removed from the vessel to a position above the cover, whereby astring of the viscous material is suspended from the probe. The probe isthen moved laterally with respect to the opening to a position offsetfrom the opening and adjacent a raised structure formed on the cover.Next, the probe is moved laterally along a path comprising movement infirst and second directions. The transition from movement in the firstdirection to movement in the second direction causes the string ofviscous material to contact the raised structure, and the continuedmovement of the probe along the path causes at least a portion of thestring of viscous material to be separated from the probe.

In one embodiment, the raised structure includes first and secondupright, non-coplanar sides defining a corner at a transitiontherebetween, and the transition from movement in the first direction tomovement in the second causes the string of viscous material to contactthe corner of the raised structure.

In one embodiment, the first and second directions are substantially atright angles to one another, and, in another embodiment, the first andsecond directions are not at right angles to one another.

In one embodiment, after moving the probe laterally with respect to theopening to a position offset from the opening and adjacent the raisedstructure, the probe is lowered so that the distal end thereof isdisposed below the top of the raised structure.

In one embodiment, the probe comprises a barrel with a protective tipmounted on a distal end thereof.

Further aspects of the invention are embodied in a system fortransferring viscous materials. The system comprises a sample holdingarea, an automated pipettor, and a controller. The sample holding areais configured to receive and position a plurality of receptacles andincludes a cover member having a plurality of openings through which theautomated pipettor can access the receptacles positioned beneath thecover member. The openings are arranged so that each opening isassociated with one of the receptacles, and a top side of the covermember includes a plurality of raised structures. Each raised structureis adjacent to one of the openings. The automated pipettor isoperatively associated with the sample holding area and is configuredfor automated movement with respect to the sample holding area andincludes a fluid transfer probe. The controller controls movement of theprobe of the pipettor, and is programmed to selectively move the probeinto a position aligned with one of the openings, lower the probethrough the opening and into the associated receptacle below theopening, raise the probe out of the associated receptacle to a positionabove the cover member, move the probe laterally to a position offsetfrom the opening and adjacent the raised structure associated with theopening with the distal end of the probe disposed below a top surface ofthe associated raised structure, and move the probe laterally, relativeto the associated raised structure, along a path comprising movement infirst and second directions, the transition from the first direction tothe second direction causing the string of viscous material suspendedfrom the probe to contact the raised structure.

In one embodiment, the probe comprises a barrel with a protective tipmounted on a distal end thereof.

In one embodiment, the controller is programmed to move the probe infirst and second directions that are substantially at right angles toone another, and, in another embodiment, the controller is programmed tomove the probe in first and second directions that are not at rightangles to one another.

In one embodiment, the controller is programmed to lower the probe aftermoving the probe to the position offset from the opening so that thedistal end thereof is disposed below the top of the raised structure.

In one embodiment, the plurality of openings are arranged in an arraypattern of aligned rows and columns of openings.

In one embodiment, each raised structure comprises two opposed andgenerally parallel sides and an end wall spanning the ends of the twosides. In another embodiment, each raised structure further comprises araised ledge spanning ends of the two sides opposite the end wall, andthe sides and the end wall are higher than the raised ledge.

In one embodiment, each raised structure is a U-shaped structure atleast partially surrounding the opening, and movement of the probelaterally with respect to the opening to a position offset from theopening comprises moving the probe through an opening defined betweenopposed legs of the U-shaped structure.

In other embodiments, each raised structure may comprises a squareelement surrounding the opening, a triangular element surrounding theopening, or a hexagonal element surrounding the opening.

In one embodiment, each raised structure comprises a raised surfacesurrounding the opening and a post projecting above the raised surfaceadjacent the opening.

In one embodiment, the system further includes a cooling systemconstructed and arranged to maintain the sample holding area a coolerthan ambient temperature.

In one embodiment, the system further includes a label reading deviceconstructed and arranged to a read machine readable label placed on eachof said receptacles.

In one embodiment, the label reading device comprises a barcode reader.

In one embodiment, the system further includes one or more receptacleholders, each configured to hold a plurality of receptacles, and thesample receiving area is configured to receive said receptacle holdersand includes guide structures to ensure the proper position andorientation of the receptacles carried in each rack relative to theopenings formed in said cover member.

In one embodiment, the guide structures define two or more lanesconfigured to receive a different one of the receptacle holders.

In one embodiment, the raised structure comprises two generally upright,non-coplanar sides defining a corner at a transition therebetween, andthe controller is programmed to selectively move the probe laterally,relative to the corner of the associated raised structure, along thepath comprising movement in first and second directions, and wherein thetransition from the first direction to the second direction causes thestring of viscous material suspended from the probe to contact thecorner of the associated raised structure

In one embodiment, the system further includes indicator elements incommunication with said controller and configured to indicate which oftwo or more lanes is to receive the next receptacle holder to beinserted into the sample receiving area.

In one embodiment, the system further includes a rack sensing elementconfigured to detect if a rack is fully inserted into the samplereceiving area.

In one embodiment, the plurality of openings are arranged in parallelrows with openings in adjacent rows being offset from one another.

In one embodiment, the sample holding area comprises a sample bay havingfirst and second side walls and a back wall extending between said firstand second side wall, and first and second side walls and said back wallsupport said cover member.

In one embodiment, the first and second side walls and said back wallare insulated.

In one embodiment, the system further includes a floor plate with acoolant tube arranged below said floor plate and configured to carry acooling medium for cooling said sample bay.

Further aspects of the invention are embodied in a sample rack forcarrying a plurality of receptacles, which may be of different sizes.The sample rack includes a receptacle holder and a cover configured tobe releasably secured to the receptacle holder. The receptacle holderincludes a plurality of receptacle-receiving pockets, a receptaclepositioning feature associated with each of said receptacle-receivingpockets, and a resilient element associated with each of saidreceptacle-receiving pockets. Each receptacle-receiving pocket isconfigured to receive a receptacle, and each resilient element isconfigured to urge the receptacle into said positioning feature to holdthe receptacle in a fixed, predetermined position within saidreceptacle-receiving pocket. The cover includes a transverse wallincluding a plurality of spaced-apart receptacle access openings formedin said transverse wall, each receptacle access opening being associatedwith one receptacle-receiving pocket. And the cover also includes areceptacle-retaining element associated with each receptacle-receivingpocket and configured to engage a portion of the top of a receptacleurged into the predetermined position within each receptacle-receivingpocket to prevent the receptacle from being lifted out of thereceptacle-receiving pocket.

In one embodiment, the receptacle holder comprises a base and aplurality of divider walls extending upwardly at spaced-apart positionsfrom said base and defining said receptacle-receiving pockets in thespaces between adjacent pairs of divider walls. Each receptaclepositioning feature is disposed along one side of each of saidreceptacle-receiving pockets, and each resilient element is disposedalong one side of each of said receptacle-receiving pockets oppositesaid positioning feature.

In one embodiment, each positioning feature comprises a V-shaped notchformed on one side of each divider wall

In one embodiment, each resilient element comprises a spring clipincluding one portion attached to a divider wall defining one side ofthe receptacle-receiving pocket and another portion projecting from thedivider wall into the receptacle-receiving pocket.

In one embodiment, the sample rack further includes a handle associatedwith said receptacle holder.

In one embodiment, a guide slot formed is formed in a bottom side of thebase, and said guide slot is configured to engage a guide rail within anapparatus configured to receive the sample rack.

In one embodiment, the sample rack further includes a machine readablelabel.

In one embodiment, the receptacle-receiving pockets are arranged in analigned configuration.

In one embodiment, the receptacle-receiving pocket is configured toreceive a cylindrical test tube of any of a plurality of differentdiameters.

In one embodiment, the cover is made from a transparent or translucentmaterial.

In one embodiment, the cover includes opposed side walls, upper dividerwalls, and lower divider walls. The transverse wall extends between theopposed side walls with a portion of each side wall extending above saidtransverse wall and a portion of each side wall extending below saidtransverse wall. The upper divider walls project above said transversewall and extend across said transverse wall from one side wall to theother side wall with one upper divider wall disposed between eachadjacent pair of access openings. The lower divider walls project belowthe transverse wall and extend across said transverse wall from one sidewall to the other side wall with one lower divider wall disposed betweeneach adjacent pair of access openings.

In one embodiment, the receptacle retaining element associated with eachreceptacle-receiving pocket comprises a notch formed in each lowerdivider wall.

Further aspects of the invention are embodied in a method for readingmachine-readable labels disposed on receptacles carried on a receptaclerack that is placed in an apparatus comprising a plurality ofrack-receiving locations. Each rack-receiving location is configured toreceive a rack holding at least one receptacle. The apparatus furtherincludes a label-reading device configured to read a rack-identifyingmachine-readable label disposed on the rack and machine-readable labelsdisposed on the at least one receptacle held on the rack, and the labelreading device is disposed adjacent to one of the rack-receivinglocations. A rack holding at least one receptacle having a machinereadable label disposed thereon is placed in the rack-receiving locationdisposed adjacent to the label reading device. During or after placingthe rack, the machine-readable label of each receptacle having amachine-readable label is read to obtain receptacle data and therack-identifying machine readable label is read to obtain rackidentifying data. The receptacle data obtained and the rack identifyingdata obtained are stored, and the receptacle data is associated with therack identifying data. The rack is then removed from the rack-receivinglocation disposed adjacent to the label-reading device. Next, the isplaced in one of the other rack-receiving locations. During or afterplacing the rack in one of the other rack-receiving locations, therack-identifying machine readable label is read to obtain rackidentifying data. Location data identifying the rack-receiving locationin which the rack was placed is acquired. The stored receptacle datathat is associated with the rack-identifying data is retrieved, and theretrieved receptacle data is associated with the acquired location datato thereby associate the retrieved receptacle data with therack-receiving location in which the rack was placed.

In one embodiment, the method further includes the step of readingreceptacle position-identifying machine readable labels to obtainreceptacle position data for each receptacle having a machine-readablelabel.

In one embodiment, the machine-readable labels are barcode labels andthe label reading device is a barcode reader.

In one embodiment, the rack-receiving location comprises a linear trackadapted to receive a rack configured to hold a plurality of receptaclesin an aligned orientation.

In one embodiment, the method further includes the step of providing anindication of the rack-receiving location in which the rack should beplaced after removing the rack from the rack-receiving location adjacentto the label reading device, and, in another embodiment, the methodfurther includes the step of determining whether the rack was placed inthe indicated location.

In one embodiment, the method further includes the step of measuring thetime lapsed between removing the rack from the rack-receiving locationadjacent to the label reading device and placing the rack in one of theother rack-receiving locations, and, in another embodiment, whether thetime lapsed is within a specified period of time is determined.

Further aspects of the invention are embodied in an apparatus forreading machine-readable labels disposed on receptacles and associatingreceptacle data read from each machine-readable label with a locationwithin the system. The apparatus includes a plurality of rack-receivinglocations, a label reading device, and a data processing system. Each ofthe rack-receiving locations is configured to receive a rack holding atleast one receptacle. The label reading device is configured to read arack-identifying machine-readable label disposed on the rack andmachine-readable labels disposed on receptacles held on the rack, andthe label reading device is disposed adjacent to one of saidrack-receiving locations. The data processing system includes datastorage media and is configured to read the machine-readable label ofeach receptacle having a machine-readable label and read therack-identifying machine readable label when the rack is placed intosaid rack-receiving location disposed adjacent to said label readingdevice to obtain receptacle data for each receptacle having amachine-readable label and to obtain rack identifying data. The dataprocessing system stores the receptacle data and the rack identifyingdata and associates the receptacle data with the rack identifying data.The data processing system reads the rack-identifying machine readablelabel when the rack is placed in one of the other rack-receivinglocations to obtain rack identifying data. The data processing systemacquires location data identifying the other rack-receiving location inwhich the rack was placed. And the data processing system retrieves thestored receptacle data that is associated with the rack-identifying dataand associates the retrieved receptacle data with the location data tothereby associate the retrieved receptacle data with the rack-receivinglocation in which the rack was placed.

In one embodiment, the machine readable labels are barcode labels andthe label reading device is a barcode reader.

In one embodiment, each rack-receiving location comprises a linear trackadapted to receive a rack configured to hold a plurality of receptaclesin an aligned orientation.

In one embodiment, the data processing system is further configured toprovide an indication of the rack-receiving location in which a rackshould be placed.

In one embodiment, the apparatus further comprises a rack configured tohold one or more receptacles and includes a rack-identifyingmachine-readable label.

These and other features, aspects, and advantages of the presentinvention will become apparent to those skilled in the art afterconsidering the following detailed description, appended claims andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate various embodiments of the presentinvention. In the drawings, like reference numbers indicate identical orfunctionally similar elements.

FIG. 1 is an upper front perspective view of a sample receptacle moduleembodying aspects of the present invention.

FIG. 2 is an upper rear perspective view of the sample receptaclemodule.

FIG. 3 is a lower front perspective view of a sample bay of the samplereceptacle module.

FIG. 4 is a perspective view of a sample rack of the sample receptaclemodule including a receptacle holder and a cover.

FIG. 5 is a top view of the receptacle holder with the cover removed.

FIG. 6 is a side view of the sample rack, including the receptacleholder and the cover.

FIG. 7 is side view of the sample rack, including the receptacle holderand the cover, with a plurality of differently-sized sample receptaclescarried in the receptacle holder.

FIG. 8 is an enlarged upper front perspective view showing, inisolation, a single viscous string removal element of the sample baycover of FIGS. 1 and 2.

FIG. 9 is a rear upper perspective view showing, in isolation, theviscous string removal element of FIG. 8.

FIG. 10 is a partial top view of the sample bay cover of FIGS. 1 and 2showing viscous string removal elements and schematically indicating apath traveled by a sample transfer probe while moving from a sampleaccess opening formed in the cover.

FIG. 11 is a partial top view of a sample bay cover showing a firstalternative configuration of viscous string removal elements andschematically indicating a path traveled by a sample transfer probewhile moving from a sample access opening formed in the cover.

FIG. 12 is a partial top view of a sample bay cover showing a secondalternative configuration of viscous string removal elements andschematically indicating a path traveled by a sample transfer probewhile moving from a sample access opening formed in the cover.

FIG. 13 is a partial top view of a sample bay cover showing a thirdalternative configuration of viscous string removal elements andschematically indicating a path traveled by a sample transfer probewhile moving from a sample access opening formed in the cover.

FIG. 14 is a partial top view of a sample bay cover showing a fourthalternative configuration of viscous string removal elements andschematically indicating a path traveled by a sample transfer probewhile moving from a sample access opening formed in the cover.

FIG. 15 is a partial top view of a sample bay cover showing a fifthalternative configuration of viscous string removal elements andschematically indicating a path traveled by a sample transfer probewhile moving from a sample access opening formed in the cover.

FIG. 15A is a cross-section along line A-A in FIG. 15.

FIG. 16 is a flow chart illustrating a method for separating a string ofviscous material from the probe of a fluid transfer mechanism.

FIG. 17 is a schematic view of a system including a sample receptaclemodule, an automated pipettor, and a controller for controllingoperation of the pipettor and programmed to execute an algorithm tocause the pipettor to perform the method illustrated in FIG. 16.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a sample receptacle module embodying aspects of thepresent invention includes a sample bay 10 within which are disposed aplurality of sample racks 100. In the illustrated embodiment, the samplebay 10 holds up to eight sample racks 100.

As shown in FIGS. 1-3, the sample bay 10 is a box-like structure havinga first side wall 12, a second side wall 16, a back wall 18, and a floorplate 20. The walls 12, 16, and 18 may be thermally insulated. Thesample bay 10 further includes a sample bay cover 40 carried at itsedges by the walls 12, 16, and 18. A front end 32 of the sample bay 10is open to permit the sample racks 100 to be inserted into and removedfrom the sample bay 10. The floor plate 20 may further include samplerack guides 22 which engage mating guides formed in the bottom of eachsample rack 100 for accurately and repeatably positioning each rack.Holes 19 formed in back wall 18 are aligned with each sample rackposition.

Sample bay 10 further includes a barcode bracket 34 mounted to the firstside wall 12 and configured to carry a barcode reader 15 in an operativeposition with respect to a barcode window 14 formed in the first sidewall 12. The barcode reader 15 carried in the barcode bracket 34 isconfigured to read barcodes placed on individual sample receptaclescarried in each of the sample racks 100 as well as barcodes on thesample racks 100 themselves. The barcodes are read through the barcodewindow 14 as the sample rack is pushed into or removed from the samplebay 10. A procedure for reading the barcodes on sample receptacles swill be described below.

The interior of the sample bay 10 is preferably kept at a cooler thanambient temperature by means of a coolant medium flowing through acoolant tube 30 arranged beneath the floor plate 20, as shown in FIG. 3.The coolant medium, which may comprise chilled water, is passed throughthe coolant tube 30 via a coolant inlet connector 28 and a coolantoutlet connector 26 mounted behind the back wall 18, as shown in FIG. 2.

The chilled interior of the sample bay 10 can cause an accumulation ofcondensation inside the sample bay 10. To convey accumulated water awayfrom the sample bay 10, a condensation tube 36 is provided along thelower front edge of the front opening 32. The condensation tube 36includes a top longitudinal slot 38, and a front edge 24 of the floorplate 20 is bent into the slot 38 to direct excess condensationcollected on the floor plate 20 into the condensation tube 36.Condensation tube 36 conveys the collected condensation to a remotecontainer or drain (not shown).

The sample bay cover 40 has formed therein a plurality of samplereceptacle access openings 42, which, in the illustrated embodiment, arearranged in a rectangular array of rows and columns, each column ofopenings aligning with the position of a sample rack 100. A raisedelement, referred to as a viscous string removal element 44, is providedadjacent each access opening 42. The function of the viscous stringremoval elements 44 will be described below.

The sample rack 100 is shown in further detail in FIGS. 4-7. Sample rack100 is adapted to receive and hold a plurality of receptacles, which, incertain embodiments, may comprise tubular containers, such as testtubes. Sample rack 100 includes a receptacle holder 102 and a cover 130.The receptacle holder 102 includes a handle 104 for grasping andcarrying the sample rack 102 and for inserting the receptacle holder 102into or removing the receptacle holder 102 from the sample bay 10. Inone embodiment, a machine-readable label, such as a barcode 103, isprovided on the receptacle holder 102, such as near the handle 104 asshown.

The receptacle holder 102 may be made from a suitable, non-reactivematerial, such as plastic or Delrin® acetyl resin, and includes a base106 extending longitudinally from the handle 104. A guide track 108 isformed in the base 106 for engaging the sample rack guides 22 providedin the floor plate 20 of the sample bay 10 to ensure proper positioningof the sample rack 100 within the sample bay 10. An alignment slot 118is formed in a top edge above the handle 104. Alignment slot 118 engagesone of the alignment projections 60 formed along the bottom of a frontedge of the sample bay cover 40 (See FIG. 3). A plurality of verticallyoriented divider walls 110 extend upwardly, at spaced intervals, fromthe base 106. The upper portions of the divider walls 110 are held infixed relative positions by a side panel 122 extending longitudinallyfrom the handle 104 to an end wall 120 along one side of the receptacleholder 102. The gap between each pair of adjacent divider walls 110defines a sample receptacle pocket 124, or receptacle-receiving area,for receiving an individual receptacle. In one embodiment,pocket-identifying indicia, such as barcode 125, is provided on thedivider walls 110 adjacent each pocket 124. The indicia, which may alsoinclude an alphanumeric identifier, “A”, “B”, “C”, etc., uniquelyidentifies each pocket 124. A machine readable label, such as “emptypocket” barcode 123, may be provided within each pocket 124, on theinner side of surface panel 122 to uniquely identify each pocket and toindicate when a receptacle is not present in the pocket 124.

A resilient element, such as a spring clip 116, is provided in eachsample receptacle pocket 124. Spring clip 116 comprises a bent element(made of, e.g., spring stainless steel) with one portion attached to onedivider wall 110 defining a receptacle pocket 124 and another portionextending at an acute angle into the pocket. Each sample receptaclepocket 124 can accommodate receptacles of varying sizes. The receptacleis held in a relatively secure, fixed position within the pocket 124 bymeans of the spring clip 116 which urges the receptacle toward a dividerwall 110 forming one side of the sample receptacle pocket 124. As shownin FIG. 5, each divider wall 110 incorporates a positioning feature,such as a shallow V-shaped notch 126, which assists in positioning(e.g., centering) a receptacle urged against the divider wall 110 by thespring clip 116. FIGS. 4 and 7 show the receptacle holder 102 carrying aplurality of large receptacles 160, small receptacles 162, andmedium-sized, capped receptacles 164. In one embodiment, the receptaclesare test tubes ranging in size from 12 mm to 16 mm in diameter.

Cover 130 fits over the top ends of the sample receptacles projectingabove the receptacle holder 102, and is preferably made from atransparent or translucent plastic material so that the contents of thereceptacle holder 102 can be observed without removing the cover 130.The cover 130 includes first and second longitudinal side walls 132, 134and end walls 136, 138. The cover 130 may include structural elementsfor realeasably securing the cover 130 to the receptacle holder 102. Inthe illustrated embodiment, the cover includes locking forks 140, 142 atopposite ends of the cover 130 (See FIG. 4) which engage mating elements(not shown) formed in the receptacle holder 102 for realeasably securingthe cover 130 to the receptacle holder 102. In one embodiment, cover 130includes a machine-readable label, such as barcode 131.

A horizontal transverse wall 144 extends between the side and end walls132, 134, 136, 138 below the topmost edges of the side and end walls,thereby defining a trough 156 in the upper portion of the cover 130. Aplurality of longitudinally-spaced access openings 146 are formed in thetransverse wall 144 and upper divider walls 148 extend laterally betweenthe side walls 132, 134 between each of the access openings 146. Eachupper divider wall 148 includes a rectangular notch 150 formed in anupper, central portion thereof. Lower divider walls 152 extend laterallybetween the side walls 132, 134 below the transverse wall 144 atpositions between the access openings 146. The space between consecutivelower divider walls 152 is large enough to accommodate the width (e.g.,diameter) of the largest receptacle that can be carried in a samplereceptacle pocket 124 (see large tubes 160 in FIG. 7). The cover 130further includes a receptacle-retaining element configured to engage aportion of the top of certain-sized receptacles urged into a centered,or other predetermined, position within each receptacle pocket 124 bythe spring clip 116 and the V-shaped notch 126. More specifically, inthe illustrated embodiment, each lower divider wall 152 includes a capnotch 154 extending across the divider wall 152 at a lower end thereof.The cap notch 154 accommodates a receptacle cap when the cover 130 isplaced over a receptacle holder 102 carrying one or more cappedreceptacles 164 (see FIG. 7).

Capped receptacles 164 may comprise receptacles provided with a cap thatis penetrable by the probe of a fluid transfer mechanism, such asdescribed in U.S. Pat. No. 6,893,612 or U.S. Pat. No. 7,435,389. Theprobe penetrates the cap by puncturing one or more piercable members ofthe cap as the probe is moved into the receptacle. The cap may alsoinclude a filter element through which the probe must pass beforereaching a fluid contained within the receptacle 164. After the probepenetrates the cap, friction between the penetrated portions of the capand/or the filter element and the probe can cause the receptacle 164 tolift out of its pocket when the probe is withdrawn from the receptacle164. The cap notch 154 of the cover 130 applies a downward holding forceon the capped receptacle 164 to prevent the receptacle 164 from beinglifted out of the receptacle pocket 124 when a probe that has penetratedthe cap is withdrawn from the receptacle 164.

A home pin 114 extends from the end wall 120. Home pin 114 lets theinstrument know that the sample rack has been fully inserted into thesample bay 10, or when it is being removed, for example by extendingthrough holes 19 formed in back wall 18 and engaging a sensor, such as aslotted optical sensor (not shown) mounted to the back wall 18. Home pin114 may also function as a positioning element to assure the rack isabsolutely vertical.

The sample rack 100 is placed within the sample bay 10 by positioningthe sample rack 100 in an aligned orientation with respect to the samplerack guides 22 provided on the floor plate 20 of the sample bay 10. Asnoted, sensors may be provided for detecting the presence of a samplerack 100 and to indicate whether the sample rack 100 is fully insertedinto the sample bay 10.

Receptacles are placed in the sample rack so that machine-readablelabels (e.g., barcodes 163, see FIG. 7) as well as human-readable labelsare visible through the side opening of each pocket 124 between adjacentdivider walls 110. As a sample rack 100 is inserted into the sample bay10, the barcode reader 15 reads each barcode 163 sequentially as thereceptacles 160, 162, and/or 164 carried in the receptacle holder 102pass the barcode window 14. If a pocket 124 is empty, the barcode 123 isread, indicating the absence of a receptacle in the pocket 124. Eachpocket-identifying barcode 125 is also read by the barcode reader 15 toprovide pocket identification data with which to associate thereceptacle (or absence of a receptacle) carried in the correspondingpocket 124. Preferably only one barcode reader is provided and,therefore, as can be appreciated from FIG. 1, it will be necessary tofill sample rack lanes (defined by the sample rack guides 22) movingfrom left to right so that there is no carrier between the carrier beinginserted and the barcode window 14 and barcode reader 15. Indicatorlights at each of the lanes may illuminate sequentially as an indicationto the operator as to which lane should be loaded next. The barcodeinformation for each receptacle is stored (e.g., in the memory of aninstrument computer controller (not shown)), and that information iscorrelated with the carrier position (i.e., lane) within the sample bay10. The barcode reader also reads the sample holder barcode 103 toidentify the holder 102 and the cover bar code 131 to ensure that thecover 130 is in place.

Occasionally, receptacles are labeled with barcodes of relatively poorquality that can be read only by a barcode reader that is in relativelyclose proximity to the barcodes. For such situations, the sample bay 10and instrument controller preferable provide a “high resolution readingmode” (“HRM”), referred to as the high resolution reading mode becauseit is in this mode in which the barcode reader 15 can read in thehighest resolution (i.e., smallest line size). HRM is preferablyoperator-selectable. After HRM is selected, the sample rack 100 loadedwith receptacles 160, 162, and/or 164 with barcodes 163 is firstinserted in the far right-hand sample rack lane, closest to the barcodereader 15 and window 14 (this will be referred to as the high resolutionreading lane). An audible and/or visible indicator may be provided toidentify the high resolution reading lane. As the sample rack 100 isinserted into the high resolution reading lane, each receptacle barcode163 is read and receptacle data obtained by reading the barcode 163 isstored. Pocket-identifier barcodes 125 and a rack identifier barcode 102are read and stored as well. The pocket-identifier data and therack-identifier data are associated with the receptacle data obtainedfor each of the receptacles in the rack, for example in a relationaldatabase. The close proximity of the high resolution reading lane to thebarcode reader 15 will increase the likelihood of an accurate read.After the sample rack 100 has been fully inserted into the highresolution reading lane, the sample rack 100 is then withdrawn. A sensormay be provided to sense when the sample rack 100 has been fullyinserted, and an indicator light and/or audible tone may signal to theoperator that the sample rack 100 may be removed. After the sample rack100 is removed, it is then re-inserted into one of the other, availablelanes. An indicator light may be provided to identify the lane intowhich the sample rack 100 is to be inserted. As the sample rack 100 isinserted into the available lane, the barcodes 163 on the receptaclesare not re-read, but the sample rack identifier barcode 103 is read toconfirm that the sample rack 100 that was just scanned in the highresolution reading lane is being inserted. The cover barcode 131 mayalso be read to ensure the positioning of the cover 130. The receptacledata associated in the database with that rack identification thenbecomes associated with that lane. The controller may be configured toerase or otherwise disable the barcodes if the sample rack 100 is notre-inserted into an available lane within a specified period of time(e.g., 5 seconds). Thus, if the sample rack 100 is not re-inserted intothe sample bay 10 within the specified period of time, the controllerwill not recognize the sample rack 100 as having been previously scannedin the high resolution reading lane, and the sample rack 100 will haveto be scanned in the high resolution reading lane again. This controlfeature will minimize the ability to switch one or more un-scannedreceptacles for scanned receptacles in the time between withdrawing thesample rack 100 from the high resolution reading lane and reinsertingthe sample rack 100 into another available lane.

After the sample rack 100 is inserted into the sample bay 10, samplematerial contained in receptacles carried in the sample rack 100 can beaccessed via a fluid transfer mechanism—such as the probe (e.g., abarrel with a protective tip, such as a pipette tip, mounted thereon) ofan automated, robotically operated pipetting device—through the accessopenings 42 formed in the sample bay cover 40 and the access openings146 formed in the cover 130. Sample material may include, for example,urine, blood, plasma, saliva, mucus, seminal fluid, amniotic fluid,cerebrospinal fluid, synovial fluid, cultures, and the like. When aprobe of a pipetting device is submerged in a viscous sample materialcarried in a receptacle and then withdrawn, a viscous string of thesample material may result in a string of viscous material beingsuspended from a distal end of the probe after the probe is withdrawnfrom the sample receptacle. Further movement of the sample transferprobe may drag the string of viscous material along with it, therebypotentially causing cross-contamination should a portion of the stringof viscous material fall into another sample receptacle or a reactionreceptacle or contact a contamination sensitive surface or component.Accordingly, the sample bay cover 40 includes viscous string removalelements 44 adjacent to each sample receptacle access opening 42, andrelative movement of the sample transfer probe in a prescribed mannerwith respect to the viscous string removal element will remove thestring of viscous material in a controlled manner at a known locationand in such a way as to prevent the string of viscous material fromfalling into another sample receptacle.

Details of the viscous string removal element 44 are shown in FIGS. 8and 9. According to one embodiment, the viscous string removal element44 comprises a generally square, U-shaped raised element at leastpartially surrounding each sample receptacle access opening 42. Theelement 44 includes side surfaces 48, 50 and a back surface 46 thatsurround the access opening 42 on three sides. End surfaces 52, 54 arelocated on either side of the open end of the U-shaped element, and acorner 56 defines a transition, or edge, between the side surface 48 andone of the end surfaces 52. A raised ledge 58 extends adjacent to theaccess opening 42 across the open end of the U-shaped element 44. Corner56 is set back from the edge of raised ledge 58 to allow more room forthe pipettor to travel between adjacent U-shaped elements. In oneembodiment the removal element 44 is 17 mm wide, 17 mm long, 8 mm high,with the raised ledge 58 that is 1 mm high. The opening 42 is 13.8 mm indiameter. The gap width between side-by-side adjacent removal elements44 is 8 mm, while the gap between lengthwise adjacent removal elements44 is 5 mm. The raised edge 58 has a length (or depth) of 2 mm, so thedistance between the back surface 46 of one element 44 and the endsurfaces 52, 54 is 7 mm.

The manner in which the viscous string removal elements 44 are used toremove a string of viscous material suspended from a probe will bedescribed with reference to FIG. 10. As shown in FIG. 10, which shows aportion of the sample bay cover 40, the probe is at position 200 when itis first withdrawn from the sample receptacle access opening 42. Theprobe is then moved with respect to the access opening 42 and theelement 44 along a path that includes a first segment 202 to a position204 that is offset from (i.e., not aligned with) the access opening 42.The path of the probe next includes a second leg 206 to a third position208 and then a third leg 210 between adjacent rows of removal elements44. Note that after moving from position 200 to position 204 offset fromthe access opening 42, the probe does not again move over any otheraccess opening in the cover 40.

While the probe moves along the path encompassing segments 202, 206, and210, any string of viscous material suspended from the probe will bedragged behind the probe (relative to the direction of probe movement)and extend in a direction generally opposite the direction of movementof the probe. A change in direction of the probe caused by thetransition from second leg 206 to third leg 210 will cause the stringsuspended from the probe to contact the corner 56 of the element 44.Corner 56 preferably defines a relatively sharp edge that will createfriction between corner 56 and the string of viscous material as theprobe continues to move relative to the corner 56. Thus, furthermovement of the probe along the third leg 210 of the path, combined withthe friction between the string of viscous material and the corner 56,will cause the string of viscous material to be separated from theprobe. The raised ledge 58 provides an obstruction that will impede anymaterial falling from the probe onto the cover 40 from flowing back intoan access opening 42.

Details of a first alternative embodiment of a viscous string removalelement are shown in FIG. 11, which shows part of alternative embodimentof a sample bay cover 40 a. The viscous string removal element,designated by reference number 220, comprises a generally square raisedelement surrounding each sample receptacle access opening 224. Theelement 220 includes four side surfaces 222 that surround the accessopening 224 on four sides. Corners 226 define transitions, or edges,between side surfaces 222.

Referring to FIG. 11, the probe is at position 228 when it is firstwithdrawn from the sample receptacle access opening 224. The probe isthen moved with respect to the access opening 224 and the element 220along a path that includes a first segment 230 to a position 232 that isoffset from the access opening 224. At position 232, the probe may belowered so that the lowest end of the probe (the distal end of theprobe) is below the top of the element 220. The path of the probemovement next includes a second leg 234 to a third position 236, andthen a third leg 238 between adjacent rows of removal elements 220. Thepath of the probe avoids taking the probe over any other access opening224 in the cover 40 a.

Again, as the probe moves, any string of viscous material suspended fromthe probe will be dragged behind the probe (relative to the direction ofprobe movement) and extend in a direction generally opposite thedirection of movement of the probe. A change in direction of the probecaused by the transition from second leg 234 to third leg 238 will causethe string suspended from the probe to contact the corner 226 of theelement 220. Corner 226 preferably defines a relatively sharp edge thatwill create friction between corner 226 and the string of viscousmaterial as the probe continues to move relative to the corner 226.Thus, further movement of the probe along the third leg 238 of the path,combined with the friction between the string of viscous material andthe corner 226, will cause the string of viscous material to beseparated from the probe. As can be appreciated from FIG. 11, thealigned viscous string removal elements 44 form a lane (corresponding tothe direction of leg 238) with nearly-continuous walls on opposite sidesthereof defined by the facing sides 222 of adjacent removal elements 44.The probe can move through this lane, with its distal tip located belowthe tops of the elements 44, and any material released from a distal endof the probe would be prevented from entering into the other openings.Thus, the walls 222 provide an edge 226 to break strings of viscousmaterial and also provide a shield against drips or flinging droplets.

Details of a second alternative embodiment of a viscous string removalelement are shown in FIG. 12, which shows part of alternative embodimentof a sample bay cover 40 b. The viscous string removal element,designated by reference number 240, comprises a generally triangularraised element surrounding each sample receptacle access opening 244.Removal element 240 includes three side surfaces 242 that surround theaccess opening 244. Corners 246 define transitions, or edges, betweenside surfaces 242.

Referring to FIG. 12, the probe is at position 248 when it is firstwithdrawn from the sample receptacle access opening 244. The probe isthen moved with respect to the access opening 244 and removal element240 along a path that includes a first segment 250 to a position 252that is offset from the access opening 244. At position 252, the probemay be lowered so that the lowest end of the probe is below the top ofremoval element 240. The path of the probe next includes a second leg254 to a third position 256, and then a third leg 258 between adjacentrows of removal elements 240. The path of the probe avoids taking theprobe over any other access opening 244 in the cover 40 b.

Again, as the probe moves, any string of viscous material suspended fromthe probe will be dragged behind the probe (relative to the direction ofprobe movement) and extend in a direction generally opposite thedirection of movement of the probe. A change in direction of the probecaused by the transition from second leg 254 to third leg 258 will causethe string suspended from the probe to contact the corner 246 of removalelement 240. Corner 246 preferably defines a relatively sharp edge thatwill create friction between corner 246 and the string of viscousmaterial as the probe continues to move relative to the corner 246.Thus, further movement of the probe along the third leg 258 of the path,combined with the friction between the string of viscous material andthe corner 246, will cause the string of viscous material to beseparated from the probe.

Details of a third alternative embodiment of a viscous string removalelement are shown in FIG. 13, which shows part of alternative embodimentof a sample bay cover 40 c. The viscous string removal element,designated by reference number 260, comprises a raised element in theshape of a hexagon surrounding each sample receptacle access opening264. Removal element 260 includes six side surfaces 262 that surroundthe access opening 264. Corners 266 define transitions, or edges,between the side surfaces 262.

Referring to FIG. 13, the probe is at position 268 when it is firstwithdrawn from the sample receptacle access opening 264. The probe isthen moved with respect to the access opening 264 and removal element260 along a path that includes a first segment 270 to a position 272that is offset from the access opening 264. At position 272, the probemay be lowered so that the lowest end of the probe is below the top ofremoval element 260. The path of the probe next includes a second leg274 to a third position 276, and then a third leg 278 between adjacentrows of removal elements 260. The path of the probe avoids taking theprobe over any other access opening 264 in the cover 40 c.

Again, as the probe moves, any string of viscous material suspended fromthe probe will be dragged behind the probe (relative to the direction ofprobe movement) and extend in a direction generally opposite thedirection of movement of the probe. A change in direction of the probecaused by the transition from second leg 274 to third leg 278 will causethe string suspended from the probe to contact the corner 266 of removalelement 260. Corner 266 preferably defines a relatively sharp edge thatwill create friction between corner 266 and the string of viscousmaterial as the probe continues to move relative to the corner 266.Thus, further movement of the probe along the third leg 278 of the path,combined with the friction between the string of viscous material andthe corner 266, will cause the string of viscous material to beseparated from the probe.

Details of a fourth alternative embodiment of a viscous string removalelement are shown in FIG. 14, which shows part of alternative embodimentof a sample bay cover 40 d. The viscous string removal element,designated by reference number 280, comprises a generally square raisedelement surrounding each sample receptacle access opening 284. Removalelement 280 includes four side surfaces 282 that surround the accessopening 284 on four sides. Corners 286 define transitions, or edges,between the side surfaces 282. Sample bay cover 40 d differs from samplebay cover 40 a, which also includes square viscous string removalelements 220 (See FIG. 11), in that the adjacent rows of removalelements 280 of sample bay cover 40 d are offset from each other.

Referring to FIG. 14, the probe is at position 288 when it is firstwithdrawn from the sample receptacle access opening 284. The probe isthen moved with respect to the access opening 284 and removal element280 along a path that includes a first segment 290 to a position 292that is offset from the access opening 284. At position 292, the probemay be lowered so that the lowest end of the probe is below the top ofremoval element 280. The path of the probe next includes a second leg294 to a third position 296, and then a third leg 298 in a diagonaldirection between diagonally adjacent removal elements 280. The path ofthe probe avoids taking the probe over any other access opening 284 inthe cover 40 d.

Again, as the probe moves, any string of viscous material suspended fromthe probe will be dragged behind the probe (relative to the direction ofprobe movement) and extend in a direction generally opposite thedirection of movement of the probe. A change in direction of the probecaused by the transition from second leg 294 to third leg 298 can causethe string suspended from the probe to contact the corner 286 of removalelement 280, even if that transition does not encompass a 90 degreechange in direction as shown in FIGS. 10-13. Thus, further movement ofthe probe along the third leg 298 of the path, combined with thefriction between the string of viscous material and the corner 286, willcause the string of viscous material to be separated from the probe.

Details of a fifth alternative embodiment of a viscous string removalelement are shown in FIGS. 15 and 15A, which show part of alternativeembodiment of a sample bay cover 40 e. The viscous string removalelement, designated by reference number 300, comprises a raised surface302 surrounding each sample receptacle access opening 304 and a post 306projecting above the raised surface 302. Post 306 includes side surfaces310 (four sides 310 in the illustrated embodiment) and corners 312 whichdefine transitions, or edges, between the side surfaces 310. Post 306may have any other shape that will provide an edge between non-coplanarsides of the post, such as triangular or hexagonal, in addition tosquare or rectangular. The post 306 may be positioned on the raisedsurface 302 so that one corner edge 312 of post 306 coincides with acorner edge of the raised surface 302 (not shown). On the other hand,raised surface 302 may have any shape, including shapes, such ascircular, not defining corner edges.

Referring to FIG. 15, the probe is at position 314 when it is firstwithdrawn from the sample receptacle access opening 304. The probe isthen moved with respect to the access opening 304 and removal element300 along a path that includes a first segment 316 to a position 318that is offset from the access opening 304. As can be appreciated fromFIG. 15A, raised surface 302 is a shorter structure than post 306, andthus, it is not necessary to lower the probe at position 318, as thelower end of the probe will already be below the top of post 306. Thepath of the probe next includes a second leg 320 to a third position322, and then a third leg 324 between adjacent rows of removal elements300. The path of the probe avoids taking the probe over any other accessopening 304 in the cover 40 e.

Again, as the probe moves, any string of viscous material suspended fromthe probe will be dragged behind the probe (relative to the direction ofprobe movement) and extend in a direction generally opposite thedirection of movement of the probe. A change in direction of the probecaused by the transition from second leg 320 to third leg 324 will causethe string suspended from the probe to contact the corner edge 312 ofthe post 306. Corner 312 preferably defines a relatively sharp edge thatwill create friction between corner 312 and the string of viscousmaterial as the probe continues to move relative to the corner 312.Alternatively, post 306 may be of a shape that is devoid of corneredges, such as cylindrical, in which case, the necessary friction—shouldthe cylindrical surface itself not provide sufficient friction—can becreated by knurling, flutes or other surface modifications that willincrease the friction of the exterior surface of the post. Thus, furthermovement of the probe along the third leg 324 of the path, combined withthe friction between the string of viscous material and the post 306,will cause the string of viscous material to be separated from theprobe. The raised surface 302 provides an obstruction that will impedeany material falling from the probe onto the cover 40 e from flowingback into an access opening 304.

FIG. 16 is a flow chart showing a method 330 for removing a string ofviscous material from the probe of a fluid transfer mechanism. Method330 is generally applicable to any of the embodiments shown in FIGS.10-15. In step 332, the probe is moved into a position aligned with areceptacle access opening formed in the cover member. In step 334, theprobe is lowered through the opening and into the associated receptaclelocated below the opening so that at least the distal end of the probeis submerged below the surface of the fluid contents of the receptacle.In step 336, the probe is raised out of the associated receptacle to aposition above the cover member. In step 338, the probe is movedlaterally to a position offset from the opening and adjacent the raisedstructure associated with the opening with the distal end of the probedisposed below a top surface of the associated raised structure. In step340, the probe is moved laterally, relative to a corner of theassociated raised structure, along a path comprising movement in a firstdirection. And in step 342, lateral movement of the probe, relative to acorner of the associated raised structure, is continued along the pathin a second direction to thereby cause a string of viscous materialconnected to the probe to contact the corner.

FIG. 17 is a schematic view of a system including a sample receptaclemodule 10, an automated pipettor 350, and a controller 360 forcontrolling operation of the pipettor 350. The automated pipettorincludes a probe comprising a barrel 352 on which is mounted (e.g.,frictionally) a protective tip 354 and is constructed and arranged toeffect movement of the protective tip 354, for example, X-Y-Z movement(and, optionally, rotational movement about one or more axes). Automatedpipettor 350 may include, or be connected to, a pump or other vacuumsource (not shown), such as a syringe pump (e.g., the Cavro XP 3000),for effecting suction at the protective tip 354 for drawing fluidmaterial into the protective tip 354. A suitable pipettor is disclosedin U.S. Patent Application Publication No. US 2008-0019878 A1. Suitableprotective tips include pipette tips manufactured and sold by TECAN(TECAN U.S. Inc., Research Triangle Park, N.C.) under the trade name“Disposable Tips for GENESIS Series”. In one embodiment, each tip has a1000 μl capacity and is conductive. Controller 360 communicates with theautomated pipettor via communication link 370 and may comprise acomputer processor programmed to execute an algorithm (e.g., thealgorithm represented by method 330 shown in FIG. 16 and describedabove) to control movement and operation of the pipettor.

The automated pipettor 350 may include a “self-teach” positioningcapability. Position locator elements may be provided on the sample bay10. During a self-teach procedure, the pipettor moves until it locatesthe position locator elements, and the coordinates of the positionlocator elements are stored in the controller 360. The positions of eachof the access openings 42 and viscous string removal elements (e.g.,removal elements 44) of the sample bay cover 40 relative to thepositions of the position locator elements are known. Therefore, one thecoordinates of the position locator elements are known, the coordinatesof each of the access openings 42 and removal elements 44 are known aswell.

The position locator elements may comprises locator pins (not shown) orother projections extending upwardly from the cover 40. Contact of theprotective tip 354 with the locator pins can be detected by capacitivesensing or by force detection. Preferably two position locator elementsare provided at separated positions on the sample bay 10 to facilitatedetermination of the location of the sample bay 10 and whether thesample bay 10 is skewed with respect to the orientation of the automatedpipettor 350. Alternative position locator elements may comprise halleffect sensors or slotted optical detectors.

While the present invention has been described and shown in considerabledetail with reference to certain illustrative embodiments, those skilledin the art will readily appreciate other embodiments of the presentinvention. Accordingly, the present invention is deemed to include allmodifications and variations encompassed within the spirit and scope ofthe following appended claims.

1. A method for separating a viscous material suspended from a probe ofan automated pipettor, said method comprising the steps of: (a) loweringthe probe into a receptacle through an opening formed in a coverdisposed over the receptacle, the receptacle containing a viscousmaterial; (b) drawing at least a portion of the viscous material intothe probe; (c) removing the probe from the vessel to a position abovethe cover, whereby a string of the viscous material is suspended fromthe probe; (d) moving the probe laterally with respect to the opening toa position offset from the opening and adjacent a raised structureformed on the cover; and (e) moving the probe laterally along a pathcomprising movement in first and second directions, wherein thetransition from movement in the first direction to movement in thesecond direction causes the string of viscous material to contact theraised structure, and wherein the continued movement of the probe alongthe path causes at least a portion of the string of viscous material tobe separated from the probe.
 2. The method of claim 1, wherein theraised structure includes first and second upright, non-coplanar sidesdefining a corner at a transition therebetween, and wherein thetransition from movement in the first direction to movement in thesecond direction in step (e) causes the string of viscous material tocontact the corner of the raised structure.
 3. The method of claim 1,wherein the first and second directions of step (e) are substantially atright angles to one another.
 4. The method of claim 1, wherein the firstand second directions of step (e) are not at right angles to oneanother.
 5. The method of claim 1, further comprising, after step (d),lowering the probe so that the distal end thereof is disposed below thetop of the raised structure.
 6. The method of claim 1, wherein saidprobe comprises a barrel with a protective tip mounted on a distal endthereof.
 7. A system for transferring viscous materials, said systemcomprising: a sample holding area for receiving and positioning aplurality of receptacles and comprising a cover member having aplurality of openings through which an automated pipettor can access thereceptacles positioned beneath the cover member, the openings beingarranged so that each opening is associated with one of the receptacles,wherein a top side of the cover member includes a plurality of raisedstructures, each raised structure being adjacent to one of the openings;an automated pipettor operatively associated with the sample holdingarea, the pipettor being configured for automated movement with respectto the sample holding area and including a fluid transfer probe; and acontroller for controlling movement of the probe of the pipettor, thecontroller being programmed to selectively: move the probe into aposition aligned with one of the openings; lower the probe through theopening and into the associated receptacle below the opening; raise theprobe out of the associated receptacle to a position above the covermember; move the probe laterally to a position offset from the openingand adjacent the raised structure associated with the opening with thedistal end of the probe disposed below a top surface of the associatedraised structure; and move the probe laterally, relative to theassociated raised structure, along a path comprising movement in firstand second directions, the transition from the first direction to thesecond direction causing the string of viscous material suspended fromthe probe to contact the raised structure.
 8. The system of claim 7,wherein said probe comprises a barrel with a protective tip mounted on adistal end thereof.
 9. The system of claim 7, wherein said controller isprogrammed to move the probe in first and second directions that aresubstantially at right angles to one another.
 10. The system of claim 7,wherein said controller is programmed to move the probe in first andsecond directions that are not at right angles to one another.
 11. Thesystem of claim 8, wherein said controller is further programmed tolower the probe after moving the probe to the position offset from theopening so that the distal end thereof is disposed below the top of theraised structure.
 12. The system of claim 7, wherein the plurality ofopenings are arranged in an array pattern of aligned rows and columns ofopenings.
 13. The system of claim 7, wherein each raised structurecomprises two opposed and generally parallel sides and an end wallspanning the ends of the two sides.
 14. The system of claim 13, whereineach raised structure is a U-shaped structure at least partiallysurrounding the opening, and movement of the probe laterally withrespect to the opening to a position offset from the opening comprisesmoving the probe through an opening defined between opposed legs of theU-shaped structure.
 15. The system of claim 13, wherein each raisedstructure further comprises a raised ledge spanning ends of the twosides opposite the end wall, wherein the sides and the end wall arehigher than the raised ledge.
 16. The system of claim 7, wherein eachraised structure comprises a configuration selected from the groupconsisting of a square element surrounding the opening, a triangularelement surrounding the opening, and a hexagonal element surrounding theopening.
 17. The system of claim 7, wherein each raised structurecomprises a raised surface surrounding the opening and a post projectingabove the raised surface adjacent the opening.
 18. The system of claim7, further comprising one or more receptacle holders, each configured tohold a plurality of receptacles, and wherein said sample receiving areais configured to receive said receptacle holders and includes guidestructures to ensure the proper position and orientation of thereceptacles carried in each rack relative to the openings formed in saidcover member.
 19. The system of claim 18, wherein said guide structuresdefine two or more lanes configured to receive a different one of thereceptacle holders.
 19. The system of claim 7, wherein said raisedstructure comprises two generally upright, non-coplanar sides defining acorner at a transition therebetween, and wherein the controller isprogrammed to selectively move the probe laterally, relative to thecorner of the associated raised structure, along the path comprisingmovement in first and second directions, and wherein the transition fromthe first direction to the second direction causes the string of viscousmaterial suspended from the probe to contact the corner of theassociated raised structure
 21. The system of claim 7, wherein theplurality of openings are arranged in parallel rows with openings inadjacent rows being offset from one another.
 22. The system of claim 7,wherein said sample holding area comprises a sample bay having first andsecond side walls and a back wall extending between said first andsecond side wall, wherein said first and second side walls and said backwall support said cover member.